Contact structure for electric switches



Jan. l, 1929.

. 1,697,340 G. A; BURNHAM l CONTACT STRUCTURE FOR ELECTRIC SWITCHES Filed May 2.9, 192i;-

Patented Jan. 1', 1929.

UNITED STATES ParlazN'rl OFFICE.

GEORQE A EURNHAMOF SA'UGUS, MASSACHUSETTS, MENTS, To CONDIT ELECTRICAL MANUFACTURING CORPORATION,

MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.v

ASSIGNOR, RY MSNE ASSIoN- or BOSTON,

CONTACT STRUCTURE FOR 'ELECTRIC SWITCHES.

Application med May 29, 1925. serial Nn. 33,804.

This invention relates to electricvswitches and has for an Object the provision of means f to improve the contact between the separable switch members when they are 'traversed 5 by a heavy current.

A further object is generally toimprove the construction and Operation of electric switches. r 'i Fig.' 1 isa side elevation, partly in section, of the current-conducting members of an electric switch embodying the invention. Fig. 2 is atransverse section of the shankportion of the brush-member, taken along line2-2 o Fig. 1.

Fig. 3 is a detail of a modified arrangement of the stationary and movable switch contact faces 16 against which the movable Switch member is adapted to abut.

members of Fig. t

The magnetlc reaction of an electric curkrent traversing `a sinuous` conductorfends 20 to straighten the conductor. This principle is herein utilized to improve the contact be- .tween `the stationary and movable switch .The movable switch, meinberincludes a relatively rigid conducting bar 18 which is disposed beneath and is extended .between the stationary4 switch members; and brush, or contact, 4members 20 are fixed to the ends of said bar and are adapted to engage said Stationary contact members 14.

of lamin lwhich are reflexed to orm vthe shank-'portion 22iand the yielding toe or contact-portions 24a Bands 26 may encircle the shank-portions of the brush members,

whereby to hold the laminae .in assembled form and, in addition, the laminaemay be soldered together and to the bands at the Shanks.

`The brush members are secured, prefera? "bly removably, to the opposite ends ofthe bar 18, by suitable means as ,bolts'28; in such' a manner that the toe-portions 24`thereof' are directed inwardly, toward eachother.

Fixed and removable areing members 29 and 31` respectively are carried by thel staf'tionary' and movable switch members and are arranged normally to shunt the main current carryingmembers when the Switch isclosed, and receive the circuit-interrupting are, as the switch opens under load.

As thus arranged, themovable switch member is adapted to be raised to bring` the l contact faces '30 of the brush members against the contact faces 16 of the fixed contact members with considerable pressure, and the brush members are adapted to yield inwardly against the contact pressure.

As. thus. arranged, the magnetic reaction on ytheftoe-portion 24 ofthe brush member,

by the current traversing the toe and shankportions of the brush-member, is to urge the toe-portions against the `fixed contact members; .or the effect is to increase the contact-pressure under load. The stationary and movable-switch memb'ersconstitue a U-shaped conductor, the magnetic fieldl about which, when carrying current, also tends -to increase the contact/pressure of the brush members, with increased current strength. The reaction between a stud and the toe-portion'of a brush, considered alone,

tendsto weaken the contact pressure but is overbalanced, or neutralized, at least, by the other reactions tending to improve the contact pressure. As thus arranged, Vthe e`ontact pressure between the movable and stationary switch members is enhanced'under load or, at least, the magnetic reactions tending to weaken the pressure are substantially neutralized. v

Fig. 3 illustrates a modification in which the reaction between the stud and brush is utilized to enhance the contact pressure. In Said brush members comprise a lurality this modification, the xed contact member 14a is extended approximately horizontally to that side-of the stationaryswitch member opposite the otherstationary switch mem;

ber, so that the current traverses the contact member approximately horizont-ally. The magnetic reaction between the contact mem.- ber and toe-portion of the brush thus tends to force. the toe-portion against thev fixed contact member. y y

The construction maybe otherwise modiiiedv Without' departing from the spirit of the invention. 4

I claim:

' 1.' An electric switch including 'a pair of v including said fixe Yfixed terminals, a-cooperating movable bridging member' havi and mwardly directed members -each j kof which is arrangedto engage a. separate ,one ofsaid xed'terminals and has its lamdisposed to the plane',

inati'ons transversel terminals.

2. An electric switch vincludin a pairl of vertical stationary 'switch -mem ers termi` nated in contact members `having horizontalfaces, and a movable switch`memb'er' disposedl beneath said contact'members and inbers one of which is carried at each end of' stant-ially horizontal v( :o'ntact faces disposed l to e l va0 cluding an approximately horizontal. intermediate section, -and a pair .of o posed up.

wardly and inwardly directed brush memsaid intermediate section 'and having sub;

age the horizontal Contact -aces said ed contact members.

3. An electric switch including a pair of vstationary switch members terminated in contact 'members, and a movable. switch member disposed beneath standingbrush member carried at each end of said intermediate section, each of'said a Jair of opposed' rus said contact' members and including. an approximately horizontal intermediate section, and an up brush members having upwardly and in# i wardly directed' toe-portions terminated sin' a horizontal contact face which "is disposed 4. A movable switch member-for lan elec tric switch including a horizontal intermediate supporting member, an upstanding brush member carried by and. disposed 4at each of the opposed nds of said supporting 'member,said brush members having vertical shank-portions and integral, mutually conve'rgenttoe-portions terminating in substantia ly horizontal contact faces 5. A movable switch member for an electric switch including an intermediate sup,- gorting member, and a pair of. opposed rush members spaced apart by the length of said supportin member and `having shank-portions carried by the opposed ends 

